An administrator has successfully recovered all Symantec NetBackup 7.5 catalogs, which used the only two catalog backup tapes. A number of backups have taken place and a catalog backup is run…

An administrator has successfully recovered all Symantec NetBackup 7.5 catalogs, which used the only two catalog backup tapes. A number of backups have taken place and a catalog backup is run automatically. The catalog backup fails with an error code 96. The administrator investigates and discovers that all of the tapes have been allocated. What is the cause of this error?